1. Field of the Invention
The invention relates to a combination needle type precision flow control valve and shut-off valve for gas chromatographs and other precision instruments.
2. Description of the Prior Art
In gas chromatography and other types of precision instrumentation, a needle type valve is frequently used to control the flow of fluids. Because of the extremely small area through which the fluid passes, precise adjustment of the needle valve setting to the flow desired is critical for proper operation of the instrument. This adjustment often requires a considerable amount of time and extreme care to achieve.
At the present time, this precision setting is completely lost whenever the valve is shut off and it requires time and painstaking effort to reset the needle valve to the desired adjustment.